	window.onload=function(){
		var time=0;
		var timeshow=document.getElementById("showtime");
		timing(timeshow);
     }
    
	 function forward(){
	     	top.location.history.go(-1);
	 }
     
	 function timing(timeshow){
	     	time--;
	     	if(time<0){
	     		forward();
	     	}else{
	     		timeshow.innerHTML=time.toString();
	     	}
	    	setTimeout("timing()",1000);
	 }